Attempt filing it, use a find file, and sand smooth. Might try a chain saw chain file. The very late Super Record cranks changed the way material was distributed at this region. The very very early cranks machined this regional "crack zone" away.

The cranks I have seen first hand that have failed big time failed at or near the pedal hole and at the shield logo, usually with visible localized polishing from toe straps or ankles first.